Output shafts of an extruder drive motor gearbox rotate according to a precise timing relative to each other. The precise timing is transferred to drive couplings attached to the output shafts, and then to screw shafts attached to the couplings, by tight fitting (precise tolerance) complementary splines. The complementary splines between the screw shafts and drive couplings interlock when free end portions of the screw shafts are inserted into open end portions of drive couplings at precise orientations. The precise orientations maintain the correct timing of intermeshing screws in an extruder barrel as the intermeshing screws rotate about longitudinal axes in response to drive motor force to apply shear forces to raw materials and thereby form a finished product.